Andrew Holme has created a totally made-from-scratch GPS receiver that can track up to eight satellites, all powered by FPGA. Andrew’s creation has been in the cooker since early 2011, and he has been refining it ever since.
Pictured above is the front-end, first mixer and IF amplifier of an experimental GPS receiver. The leftmost SMA is connected to a commercial antenna with integral LNA and SAW filter. A synthesized first local oscillator drives the bottom SMA. Pin headers to the right are power input and IF output. The latter is connected to a Xilinx FPGA which not only performs DSP, but also hosts a fractional-N synthesizer.
Originally designed to track four satellites (the minimum for calculating global position data), this GPS receiver has most recently been updated to track eight satellites. This upgrade not only increases the accuracy of the GPS to near-military spec, but at the same time manages to free up about 50% of the gates available on the Xilinx Spartan 3 chip he’s using by running an embedded CPU alongside it and serializing the processing.
Andrew’s GPS project goes into way more detail than we can suitably do it justice for on a blog post, so be sure to check out the project in it’s entirety, complete with all the requisite math, charts, graphs, etc. Sadly does not contain pie charts.
(via Andrew Holme’s website )